(1) Field of the Invention
The present invention relates to a method used to form a bonding pad, used to allow electrical communication between an overlying gold wire, and underlying circuitry of an integrated circuit, and more specifically to a method used to create a metal mesh pattern, underlying the bonding pad, used to increase the surface area, and the roughness of the overlying bonding pad.
(2) Description of the Prior Art
Wire bonds, physically, as well as electrically, connected to underlying circuitry, of semiconductor chips, are used to connect the specific semiconductor chip to packaging elements, such as printed circuit board, or ceramic modules. A bond pad structure, is usually formed overlying the top conductive layer, of the semiconductor chip, and used to accept an overlying metal, or gold wire bond structure. In most cases a group of metal studs are used between, and to connect the bond pad structure, to the top conductive layer, of a semiconductor chip, with the metal studs formed in via holes, that in turn have been formed in an inter-metal dielectric, (IMD), layer. However the large, exposed, surface area of IMD layer, located surrounding the smaller regions of metal studs, can result in defect formation, or cracking of the IMD layer, as a result of the large bonding force, experienced during the metal wire bonding procedure, where the large bonding forces is distributed throughout the overlying bond pad structure.
This invention will describe a process for fabricating a metal mesh pattern, to be used in place of a group of individual studs. The presence of the metal mesh pattern, creates isolated islands of IMD, reducing the area of the exposed IMD, thus reducing the bonding force on the IMD) shape. In addition the metal mesh pattern is formed with indented, or notched, top surface features, which increases the surface area of the metal mesh structures, when compared to metal mesh patterns, comprised with smooth top surface topographies. This in turn result in a roughened top surface of the overlying, bond pad structure, allowing improved bondability characteristics, for the subsequent metal, or gold wire bonds, to be realized. Prior art, such Shiue et at, in U.S. Pat. No. 5,700,735, describe the formation of, and the use of, diamond shaped via plug structures, to improve the characteristics of an overlying bond pad structure. However that prior art does not describe the metal mesh pattern, with indented, or notched top surfaces, used to allow an overlying, bond pad structure, with increased top surface roughness, to be achieved.